Systems and methods for deploying a portion of a stent using an auger-style device

ABSTRACT

The present embodiments provide systems and methods for deploying at least a portion of a stent. In one embodiment, the system comprises a cannula having an outer surface, and an auger having a plurality of turns coupled to the outer surface of the cannula. A stent has a portion dimensioned to be disposed within a valley of the auger. Rotation of the cannula and the auger advances the portion of the stent in a predetermined longitudinal direction.

PRIORITY CLAIM

This invention claims the benefit of priority of U.S. ProvisionalApplication Ser. No. 61/745,171, entitled “Systems and Methods forDeploying a Portion of a Stent Using and Auger-Style Device,” filed Dec.21, 2012, the disclosure of which is hereby incorporated by reference inits entirety.

BACKGROUND

The present embodiments relate generally to apparatus and methods fortreating medical conditions, and more specifically, to systems andmethods for deploying a portion of a stent using an auger-style device.

Stents may be inserted into an anatomical vessel or duct for variouspurposes. Stents may maintain or restore patency in a formerly blockedor constricted passageway, for example, following a balloon angioplastyprocedure. Other stents may be used for different procedures, forexample, stents placed in or about a graft have been used to hold thegraft in an open configuration to treat an aneurysm. Additionally,stents coupled to one or both ends of a graft may extend proximally ordistally away from the graft to engage a healthy portion of a vesselwall away from a diseased portion of an aneurysm to provide endovasculargraft fixation.

Stents may be either self-expanding or balloon-expandable, or they canhave characteristics of both types of stents. Self-expanding stents maybe delivered to a target site in a compressed configuration andsubsequently expanded by removing a delivery sheath, removing triggerwires and/or releasing diameter reducing ties. With self-expandingstents, the stents expand primarily based on their own expansive forcewithout the need for further mechanical expansion. In a stent made of ashape-memory alloy such as nitinol, the shape-memory alloy may beemployed to cause the stent to return to a predetermined configurationupon removal of the sheath or other device maintaining the stent in itspredeployment configuration.

When trigger wires are used as a deployment control mechanism, thetrigger wires may releasably couple the proximal and/or distal ends of astent or stent-graft to a delivery catheter. Typically, one or moretrigger wires are looped through a portion of the stent near a vertex ofthe stent. For example, trigger wires may be used to restrain a“Z-stent” or Gianturco stent comprising a series of substantiallystraight segments interconnected by a series of bent segments. Thetrigger wires may be disposed through, and pull upon, the bent segmentsto pull the stent closely against the delivery catheter.

Trigger wires also may be used in conjunction with different stentdesigns, such as cannula-cut stents having relatively acute or pointedbends. The designs of cannula-cut stents may facilitate compression ofthe stent to a relatively small delivery profile due to the tight bendsof the apices. With such stents, the trigger wires may be looped aroundone or more vertices formed beneath the proximal and/or distal apices,e.g., a location where an individual apex splits into two separate strutsegments.

If trigger wires are threaded through the vertices of such cannula-cutstents, the trigger wires may become crimped at the vertices duringcompression of the stent to a reduced diameter delivery profile. If thetrigger wires are crimped between the strut segments, the trigger wiresand/or stent segments may become damaged during delivery, particularlyfor nickel-titanium stents that may be sensitive to surfaceimperfections. Furthermore, in some instance, trigger wires may requirea relatively high deployment force when being retracted, and theprovision of multiple trigger wires may add to the profile of thedelivery system.

SUMMARY

The present embodiments provide systems and methods for deploying atleast a portion of a stent. In one embodiment, the system comprises acannula having an outer surface, and an auger having a plurality ofturns coupled to the outer surface of the cannula. A stent has a portiondimensioned to be disposed within a valley of the auger. Rotation of thecannula and the auger advances the portion of the stent in apredetermined longitudinal direction.

An enclosure may encircle the auger. The enclosure may comprise aplurality of struts separated by a plurality of slots, where the portionof the stent extends through one of the plurality of slots in a deliverystate. In one example, each of the plurality of struts and each of theplurality of slots are generally parallel to each other in a directionrunning along a longitudinal axis of the apparatus.

In one embodiment, at least one of the plurality of slots of theenclosure has proximal and distal regions and a width at the proximalregion is greater than a width at the distal region. The stent maycomprise a widened securement region that comprises a width that is lessthan a width of the proximal region of the slot and greater than a widthat the distal region of the slot. The stent further may comprise aproximal extension disposed adjacent to the widened securement region,where a width of the proximal extension is less than the width of thedistal region of the slot.

The enclosure may be circumferentially rotatable relative to thecannula. An atraumatic tip is coupled to the cannula, and at least aportion of the atraumatic tip may be disposed beneath the enclosure. Adistal stop member coupled to the cannula may be positioned adjacent toa distal end of the enclosure and allows the enclosure to rotaterelative to the cannula, but prevents the enclosure from slidingdistally over the cannula.

Other systems, methods, features and advantages of the invention willbe, or will become, apparent to one with skill in the art uponexamination of the following figures and detailed description. It isintended that all such additional systems, methods, features andadvantages be within the scope of the invention, and be encompassed bythe following claims.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention can be better understood with reference to the followingdrawings and description. The components in the figures are notnecessarily to scale, emphasis instead being placed upon illustratingthe principles of the invention. Moreover, in the figures, likereferenced numerals designate corresponding parts throughout thedifferent views.

FIG. 1 is a side view of an embodiment of a system comprising an augerand an enclosure.

FIG. 2 is a side view depicting a portion of a stent used with thesystem of FIG. 1.

FIGS. 3A-3C are, respectively, cross-sectional views of the apparatus ofFIG. 1 as taken along lines A-A, B-B and C-C.

FIG. 4 is a side-sectional view of the enclosure of FIG. 1.

FIG. 5 is a side view of the enclosure of FIG. 1.

FIG. 6 depicts an exemplary stent-graft having a portion that may bedeployed using the system of FIGS. 1-5.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the present application, the term “proximal” refers to a directionthat is generally closest to the heart during a medical procedure, whilethe term “distal” refers to a direction that is furthest from the heartduring a medical procedure.

Referring to FIGS. 1-2, a first embodiment of an apparatus 20 is shownfor deploying a portion of a stent. The apparatus 20 generally comprisesa cannula 30 having an outer surface 31, and an auger 40 having a regionthat is coupled to the outer surface 31 of the cannula 30.

The cannula 30 may be incorporated as part of a broader stent orstent-graft delivery system, and may span a longitudinal length in whicha distal segment extends outside of a patient's body, and a proximalsegment, including the auger 40, is delivered towards a target siteinside of a patient's body. The cannula 30 may be used as an innercannula, to the extent that one or more outer cannulas or sheaths aredisposed coaxially over the cannula 30. For example, a stent-graft maybe disposed over an exterior surface of the cannula 30 and within one ormore outer cannulas or sheaths, thereby encompassing the stent-graftduring a delivery stage.

The cannula 30 may comprise a tubular member having a lumen sized toallow the cannula 30 to be advanced over a wire guide during delivery. Aproximal region of the cannula 30 may be integrally formed with, orexternally coupled to, an atraumatic tip 35. The atraumatic tip 35 maycomprise proximal and distal regions 36 and 37, respectively, and acentral region 38 disposed therebetween. The proximal and distal regions36 and 37 comprise a smaller outer diameter relative to the centralregion 38, with a first taper allowing for a smooth transition betweenthe proximal region 36 and the central region 38, and a second taperallowing for a smooth transition between the distal region 37 and thecentral region 38.

The auger 40 comprises a proximal end 41, a distal end 42, a pluralityof helical turns 43 disposed therebetween, and valleys 44 disposedbetween the helical turns 43, as shown in FIGS. 1-2. As will bedescribed further below, a portion of a stent 60 may be secured withinthe valleys 44 between adjacent helical turns 43.

In one non-limiting example, the auger 40 may be secured directly to theouter surface 31 of the cannula 30 using a suitable mechanism, such as asolder, weld, mechanical attachment, friction fit, or combination ofthese or other techniques and mechanisms. Alternatively, the auger 40may be secured to an outer surface of a cylindrical supporting member,such as a steel tube, which in turn is securely disposed around theouter surface 31 of the cannula 30 using any of the aforementionedtechniques.

The exemplary auger 40 may be formed from stainless steel, nitinol,titanium, or other suitable biocompatible materials. In one example, theauger 40 is formed from a material that has radiopaque properties.

The apparatus 20 further comprises an enclosure 70 for housing the auger40. The enclosure 70 comprises a first end 71 having an outer diameterdc₁, and a second end 72 having a second outer diameter dc₂, as bestseen in FIGS. 1 and 4. It is noted that the diameter at the first end 71of the enclosure 70 can be larger to accommodate the provision of thehelical turns 43 of the auger 40, while still providing spacing betweenan outermost surface of the helical turns 43 and an inner surface of theenclosure 70 to ensure that the helical turns 43 can rotate relative tothe enclosure 70, as explained further below. A second end 72 of theenclosure 70 may be positioned distally of the auger 40, as shown inFIG. 1, and the second outer diameter dc₂ may be slightly larger thanthe outer surface 31 of the cannula 30. A taper 74 reduces the diameterof the enclosure 70 between the first end having the outer diameter dc₁and the second end having the reduced outer diameter dc₂.

In the examples shown, the first end 71 of the enclosure 70 is theproximal end, while the second end 72 of the enclosure 70 is the distalend. However, in alternative embodiments, the axial orientation of theenclosure 70 may be reversed. For example, the enclosure 70 may have thefirst end 71 of greater diameter located distally, while the second end72 of lesser diameter is located proximally, and a reverse rotationalsequence of deployment may be used relative to the manner describedherein.

The enclosure 70 further comprises a plurality of struts separated by aplurality of slots. Each of the struts and slots has proximal and distalends, and are generally parallel to each other in a direction runningalong a longitudinal axis of the apparatus, as shown in FIG. 1. In thisnon-limiting example, four struts 75 a-75 d are depicted as beingseparated by four slots 76 a-76 d, as shown in FIGS. 1-2, 3A-3C and 5.However, it will be appreciated that greater or fewer number than fourslots and four struts may be provided for coupling selected proximalapices of a stent 60 to the enclosure 70, as explained further below.

Each of the slots 76 a-76 d has proximal regions 77 and distal regions78. The proximal regions 77 have a width w₁, which is greater than awidth w₂ of the distal regions 78, as depicted in FIG. 5. The wideningof the proximal regions 77 of the slots 76 a-76 d allows a widenedsecurement region 67 of the stent 60 to be radially advanced onlythrough the proximal regions 77 of their associated slots.

In particular, the widened securement region 67 comprises a width w₃,which is less than the width w₁ of the proximal regions 77 of the slots,but greater than the width w₂ of the distal regions 78, as indicated bythe dimensions in FIGS. 5-6, and depicted in an assembled state of FIG.2. The width w₂ of the distal regions 78 of the slots 76 a-76 d isgreater than a width w₄ of proximal extensions 66 of the stent 60, whichmay be disposed adjacent to the widened securement regions 67, therebyallowing the proximal extensions 66 to extend through an associatedslot, as depicted in FIG. 2.

In one embodiment, the enclosure 70 is designed to cooperate with atleast a portion of the atraumatic tip 35. The distal region 37 of theatraumatic tip 35 may comprise an outer surface that corresponds to theshape of an inner surface at a proximal region of the enclosure 70. Inparticular, the enclosure 70 comprises a proximal inner taper 81, asshown in FIG. 4. The outer surface of the distal region 37 of theatraumatic tip 35 generally annularly abuts the proximal inner taper 81in the assembled state of FIGS. 1-2.

In accordance with one aspect, the enclosure 70 can rotatecircumferentially relative to the atraumatic tip 35 and the cannula 30.Notably, the proximal inner taper 81 of the enclosure 70 is disposedaround the distal region 37 of the atraumatic tip 35, while the distalend 72 of the enclosure 70 is disposed around the outer surface 31 ofthe cannula 30. Since the proximal and distal regions of the enclosure70 are not secured to the atraumatic tip 35 and the cannula 30,respectively, the enclosure 70 can rotate circumferentially relative tothese components.

A distal stop member 79 may be positioned adjacent to the distal end 72of the enclosure 70, as shown in FIG. 1. The distal stop member 79allows the enclosure 70 to rotate relative to the cannula 30, butprevents the enclosure 70 from sliding distally over the cannula 30. Thedistal stop member 79 may be formed integrally with the cannula 30, oras an external component secured to the outer surface 31 of the cannula,and may comprise any suitable biocompatible material.

The proximal inner taper 81 of the enclosure 70 extends inward to anopening 82, shown in FIG. 4, which has a diameter that allows passage ofthe cannula 30 so that the cannula 30 can be coupled to the atraumatictip 35. Moreover, a stepped surface 83 is provided at select locationsjust distal to the opening 82, as shown in FIG. 4. The stepped surface83 may be generally perpendicular to the longitudinal axis of thecannula 30. The stepped surface 83 may be positioned in the spaces thatare in-between the slots 76 a-76 d, as depicted in FIG. 5. In otherwords, the stepped surface 83 is positioned only beneath the pluralityof struts 75 a-75 d, and therefore, does not impede advancement ofstruts of the stent 60 through the slots 76 a-76 d. The stepped surface83 may reduce the possibility that the struts of the stent 60 becomeinadvertently lodged under the struts 75 a-75 d of the enclosure 70.Preferably, the proximal end 41 of the auger 40 is disposed immediatelyadjacent to the stepped surface 83 of the enclosure 70, as depicted inFIG. 1.

The enclosure 70 further comprises a main housing 84, which is disposedbetween the stepped surface 83 and the distal end 72, as shown in FIG.4. The main housing 84 is sized for housing the auger 40 therein, aridhas an inner diameter that remains larger than the auger along itslongitudinal length, thereby permitting rotation of the auger 40 withinthe main housing 84.

The enclosure 70 may be formed from stainless steel, nitinol, polymers,or other suitable biocompatible materials. Moreover, the enclosure 70may be manufactured as a single component, or multiple components thatare secured together. In one embodiment, the enclosure 70 may bemanufactured by forming an outer shell of material, and then insertingmaterial that forms the proximal inner taper 81 and the stepped surface83, and separately cutting the slots 76 a-76 d into the outer shell.

Referring to FIG. 6, an exemplary stent-graft 50, which may be deployedusing the apparatus 20 of FIGS. 1-5, has a proximally-located stent 60coupled to the graft material 90. In this non-limiting embodiment, thestent 60 may be manufactured from a continuous cylinder into which apattern may be cut by a laser or by chemical etching to produce slits inthe wall of the cylinder. The resulting structure may then be heat setto give it a desired final configuration.

The stent 60 has proximal and distal ends 61 and 62, a series ofproximal apices 63 disposed near the proximal end 61 of the stent 60,and a series of distal apices 69 disposed near the distal end 62 of thestent 60. A plurality of strut segments 72 and 73 are disposed betweenthe series of proximal apices 63 and the series of distal apices 69, asshown in FIG. 6. The series of proximal apices 63 are each disposedproximally beyond a proximal end 92 of the graft 90, and the series ofdistal apices 69 of the stent 60 are each disposed distal to theproximal end 92 of the graft 90.

In FIG. 6, each of the proximal apices 63 comprise an end region 64having an integral barb 77 formed therein. The barb 77 may be formed bylaser cutting a desired barb shape into the end regions 64. A slit 76therefore is formed into each end region 64 after the desired barb shapeis formed, as shown in FIG. 6. Once the desired barb shape is cut, amain body of the barb 77 may be bent in a radially outward directionwith respect to the end region 64. The angle may comprise any acuteangle, or alternatively may be substantially orthogonal or obtuse. Ifdesired, the barb 77 may be sharpened, for example, by grinding the tipof the barb, to facilitate engagement at a target tissue site.

In FIG. 6, at least one pair of adjacent, proximal apices 63 maycomprise different features. In particular, alternating proximal apices63 terminate at the end regions 64 housing the barbs 77. However, otheralternating proximal apices 63 a and 63 b have coupling regionsextending proximally beyond the end regions 64. The coupling regions ofthe proximal apices 63 a and 63 b comprise the narrower proximalextensions 66 and the widened securement regions 67, as shown in FIG. 6.For this exemplary stent 60, a total of eight proximal apices areprovided around the circumference of the stent, though only four apicesare depicted in the side view of FIG. 6 for illustrative purposes.Accordingly, in the example having a total of eight proximal apices withalternating features, four of the apices around the circumference of thestent will comprise only proximal apices 63 that terminate at the endregions 64 housing the barbs 77, while the other four proximal apiceswill have the coupling regions comprising the narrower proximalextensions 66 and the widened securement regions 67, as depicted by theproximal apices 63 a and 63 b in the side view of FIG. 6. In thisexample, the coupling regions of the proximal apices 63 a and 63 b arecoupled to the slots 76 a and 76 b of the enclosure 70, as depicted inFIG. 2, while two other proximal apices having coupling regions would becoupled to the slots 76 c and 76 d in a similar manner.

For the exemplary stent of FIG. 6, when the proximal apices havingcoupling regions are secured within the enclosure 70, it should be notedthat the alternating proximal apices 63 without coupling regions (i.e.,those terminating at the end regions 64) may be pulled radially inwardin an indirect manner by the strut segments 72 and 73, which are commonto adjacent apices. In this manner, all of the proximal apices of thestent 60 may be partially or fully restrained during delivery.

For illustrative purposes, it should be noted that the alternatingproximal apices 63 without coupling regions (i.e., those terminating atthe end regions 64) are not depicted in FIG. 2; rather, FIG. 2 depictsthe presence of only proximal apices having coupling regions comprisingthe narrower proximal extensions 66 and the widened securement regions67. In alternative embodiments, however, each of the proximal apices ofthe stent 60 may in fact be provided with such coupling regions.Moreover, in further alternatives, the coupling regions need not belocated on the proximal apices, but may be positioned on other regionsof the stent.

Referring still to FIG. 6, the first and second angled strut segments 72and 73 meet with one another distally to form a distal transition region85. In the embodiment of FIG. 6, each of the distal apices 69 comprisesan end region 88 having a suture bore 89 formed therein. Further, eachof the distal apices 69 comprises an imaging bore 87 adapted to receivean imaging element 87 a, such as a radiopaque marker. The imaging bore87 is disposed proximal to the suture bore 89, and the imaging bore 87is adapted to be aligned with the proximal end 92 of the graft 90,thereby allowing the imaging element 87 a associated with the imagingbore 87 to significantly enhance imaging directly at the proximal end 92of the graft 90. Further, the stent 60 may comprises at least one barb86 that is integrally formed along the distal transition region 85 at alocation proximal to the imaging bore 87, as shown in FIG. 6.

In this manner, the stent 60 may be used as an attachment stent forendovascular graft fixation. For example, the graft material 90 mayoverlap with an aneurysm to seal off fluid flow into the aneurysm, whilethe proximal end 61 of the stent 60 may extend in a proximal directionaway from the graft material, e.g., to engage a healthy portion of avessel wall away from a diseased portion of the aneurysm. As will beapparent, one or more additional stents may be coupled to an inner orouter surface of the graft material 90, i.e., at a location distal tothe stent 60, to help maintain patency throughout the graft material.

Expansion of the stent 60 is at least partly provided by the angledstrut segments 72 and 73, which may be substantially parallel to oneanother in a compressed state, but may tend to bow outward away from oneanother in the expanded state shown in FIG. 6. The stent 60 may beformed from any suitable material, such as a laser-cut nitinol cannula.If manufactured from nitinol, the stent 60 may be inclined to assume theexpanded state shown in FIG. 6 upon removal of a delivery sheath orengagement with the enclosure 70, as explained above.

The stent 60 has a reduced diameter delivery state so that it may beadvanced to a target location within a vessel or duct. The stent 60 alsohas an expanded deployed state to apply a radially outward force upon atleast a portion of a vessel or duct, e.g., to maintain patency within apassageway, or to hold open the lumen of a graft. In the expanded state,fluid flow is allowed through a central lumen of the stent 60. Further,the struts of the stent 60 may comprise a substantially flat wireprofile or may comprise a rounded profile. As best seen in FIG. 2, thestruts of the stent 60 generally comprise a flat wire profile.

The stent 60 may be manufactured from a super-elastic material. Solelyby way of example, the super-elastic material may comprise ashape-memory alloy, such as a nickel titanium alloy (nitinol). If thestent 60 comprises a self-expanding material such as nitinol, the stentmay be heat-set into the desired expanded state, whereby the stent 60can assume a relaxed configuration in which it assumes the preconfiguredfirst expanded inner diameter upon application of a certain cold or hotmedium. Alternatively, the stent 60 may be made from other metals andalloys that allow the stent 60 to return to its original, expandedconfiguration upon deployment, without inducing a permanent strain onthe material due to compression. Solely by way of example, the stent 60may comprise other materials such as stainless steel, cobalt-chromealloys, amorphous metals, tantalum, platinum, gold and titanium. Thestent 60 also may be made from non-metallic materials, such asthermoplastics and other polymers.

In an exemplary method of use, the proximal apices 63 of the stent 60having coupling regions are secured through the slots 76 a-76 d in adelivery state, as shown in FIG. 2. For example, the first proximal apex63 a may be positioned over the slot 76 a, and the widened securementregion 67 of the first proximal apex 63 a may be aligned with, andpressed radially within, the widened proximal region 77 of the slot 76a. The proximal apex 63 a may be pushed radially inward and held steady,while the cannula 30 and the auger 40 are rotated in a first direction,thereby allowing the widened securement region 67 of the proximal apex63 a to be advanced in a proximal to distal direction by the auger 40.At this time, the widened securement region 67 is positioned withinvalleys 44 between adjacent helical turns 43, and the narrower proximalextension 66 extends radially through the slot 76 a, as shown in FIG. 2.Notably, since the widened securement region 67 comprises the width w₃,which is greater than the width W₂ of the distal region 78 of the slot76 a, as explained above, the widened securement region 67 is capturedradially within the slot 76 a, despite any tendency for this portion ofthe stent 60 to want to self-expand radially outward. Optionally, thewidened securement region 67 may comprise a concave end surface 68, asshown in FIG. 6, which may follow the contour of the valleys 44 betweenthe helical turns 43 of the auger 40 in the delivery state.

Similarly, a second proximal apex 63 b may be positioned over the slot76 b, as depicted in FIG. 2, and the widened securement region 67 may bealigned with, and pressed radially within, the widened proximal region77 of the slot 76 b, while the cannula 30 and the auger 40 are rotatedin the first direction to advance the widened securement region 67 ofthe second proximal apex 63 b in a proximal to distal direction by theauger 40. This process may be repeated until all of the proximal apicesof the stent 60 having such coupling regions are secured within theenclosure 70 through the slots, in the manner shown in FIG. 2.

The coupling shown in FIG. 2 secures portions of the stent 60 within theenclosure 70 in a manner that may subsequently facilitate insertion ofthe subassembly comprising the cannula 30 and the stent-graft 50 into anouter sheath. As will be apparent, the outer sheath is configured toradially restrain other regions of the stent-graft 50 for delivery to atarget site within a patient's anatomy, as described in the exemplarysequence below.

An introducer, similar to that described in PCT application WO98/5761,entitled “A Prosthesis and a Method and Means of Deploying aProsthesis,” which is incorporated herein by reference in its entirety,may be used to deploy the stent-graft 50. PCT application WO98/5761describes a deployment system for an endoluminal prosthesis whereby theprosthesis is radially compressed onto a delivery catheter and iscovered by an outer sheath. To deploy the system, the operator slides orretracts the outer sheath over the delivery catheter, thereby exposingthe prosthesis. The prosthesis expands outwardly upon removal of thesheath. The operator can directly manipulate the sheath and the deliverycatheter, which provides the operator with a relatively high degree ofcontrol during the procedure. However, in the current embodiments,trigger wires and any of their associated sleeves would not be necessaryto deploy the stent-graft 50. Rather, the cannulas 30 and the auger 40of the present embodiments may be incorporated as part of the deploymentsystem with the stent-graft 50 being positioned coaxially between thecannula 30 and the outer sheath. A mechanism, such as a pin vise, may beemployed to prevent inadvertent rotation of the cannula 30 prior to theintended rotation as described in the present application.

A wire guide may be advanced to the target site, and the cannula 30 maybe advanced over the wire guide to position the apparatus 20 at thedesired location in proximity to the target site, with the atraumatictip 35 reducing the likelihood of injury to bodily passageways duringdelivery. The outer sheath is disposed over the cannula 30 and thestent-graft 50 during insertion to the target site. Upon properpositioning at the target site using a desired imaging modality, theouter sheath is then retracted to expose at least a portion of the stent60. At this time, portions of the stent 60 near the proximal end 61 thatare not held within the enclosure 70 may partially deploy radiallyoutward, thereby providing an amount of slack that may facilitatesubsequent longitudinal movement of the portions held within theenclosure 70.

When the stent 60 is at least partially exposed, and it is desirable todeploy the proximal end 61 of the stent 60, the cannula 30 may berotated in a second direction, i.e., in a reverse manner from which thewidened securement regions 67 were coupled within the enclosure 70. Inthis manner, the auger 40 is rotated in the second direction, along withthe cannula 30, to thereby advance the widened securement regions 67 ina distal to proximal direction within their respective slots 76 a-76 d.

The proximal apices 63 of the stent 60 can self-deploy in a radiallyoutward direction once the widened securement regions 67 are advancedproximally so that they are aligned with the widened proximal regions 67of their respective slots 76 a-76 d. Notably, the angled shape of thedistal region 37 of the atraumatic tip 35 may provide a ramp-likeelement to facilitate radial outward deployment of the widenedsecurement regions 67. Further, the stepped surface 83, which may bepositioned in the spaces in-between the slots 76 a-76 d, may reduce thelikelihood that the proximal apices of the stent 60 become inadvertentlylodged under the struts 75 a-75 d.

During the process of advancing the widened securement regions 67 in adistal to proximal direction within their respective slots 76 a-76 d,the cannula 30 and the enclosure 70 may be advanced distally. In thismanner, the proximal apices 63 of the stent 60 will not be pulledproximally, relative to the remainder of the stent-graft 50, in a mannerthat imposes significant strain upon the proximal apices 63 duringdeployment. Further, as noted above, an amount of slack may be providedto portions of the stent 60 after partial pullback of an outer sheath,and such slack may further reduce strain imposed upon the proximalapices during advancement by the auger 40.

After the restrained proximal apices 63 of the stent 60 self-deploy in aradially outward direction through the proximal regions 77 of the slots76 a-76 d, the remainder of the stent-graft 50 may be deployed byfurther retraction of the outer sheath or actuation of any other devicesthat are radially constraining the remainder of the stent-graft 50.

Advantageously, the proximal end 61 of the stent 60 is radiallyrestrained without the use of convention trigger wires that span a fulllongitudinal length of the delivery system. Accordingly, the radialprofile of the delivery system may be reduced without the provision ofmultiple trigger wires and one or more associated sleeves to house thetrigger wires, thereby reducing packing density of the system. Moreover,deployment may be simplified as reduced deployment forces are expectedto be needed relative to the use of conventional trigger wires.

As a further advantage, deployment of the stent 60 using the apparatus20 comprising the auger 40 may allow for more precise positioning of thestent 60. In particular, deployment using the auger 40 may provide amore controlled radial release of the associated portion of the stent60, whereas the release of conventional trigger wires may require higherdeployment forces that can cause a portion of the stent to jumplongitudinally, thereby potentially deploying the stent offset from theintended target site.

As yet a further advantage, during deployment of the stent 60, theenclosure 70 can rotate circumferentially relative to the atraumatic tip35 and the cannula 30. This allows the orientation of the enclosure 70and the proximal apices 63 to remain generally the same while thecannula 30 and the auger 40 are rotated circumferentially duringdeployment. Still further, the enclosure 70 encloses the auger 40 andreduces the possibility that the auger 40 can interfere with, damage, orsnag various endovascular, stent or graft structures during manipulationand removal of the delivery device.

In an alternative embodiment, the axial orientation of the enclosure maybe reversed, i.e., such that the widened portion of the slots 76 a-76 dresides at the distal end of the enclosure 70. In this alternative, theportion of the stent to be coupled within the enclosure 70 is loaded ina similar manner described above but with rotation of the cannula 30 andauger 40 in an opposite circumferential direction relative to theexample of FIGS. 1-2, and further, release of the coupled portion of thestent occurs in the opposite circumferential direction that achievesthis function in FIGS. 1-2.

Moreover, while one exemplary stent 60 is shown and described in FIGS. 2and 6, various alternative stent configurations may be used inconjunction with the auger 40 and the enclosure 70 of FIGS. 1-5.Further, such stents may be deployed alone, or as part of a stent-graftsystem, as depicted herein.

While various embodiments of the invention have been described, theinvention is not to be restricted except in light of the attached claimsand their equivalents. Moreover, the advantages described herein are notnecessarily the only advantages of the invention and it is notnecessarily expected that every embodiment of the invention will achieveall of the advantages described.

We claim:
 1. A system for deploying at least a portion of a stent, thesystem comprising: a cannula having an outer surface; an auger havingproximal and distal ends and a plurality of turns disposed therebetween,where the auger is coupled to the outer surface of the cannula; a stenthaving a portion dimensioned to be disposed within a valley of theauger, where rotation of the cannula and the auger advances the portionof the stent in a predetermined longitudinal direction; an enclosureencircling the auger, where the enclosure has a first end having a firstoutside dimeter and a second end having a second outside diameter, wherethe first outside diameter is larger than the second outside diameter,where the first end of the enclosure is proximal to the second end ofthe enclosure, and where the enclosure comprises a plurality of strutsseparated by a plurality of slots, where the portion of the stentextends through one of the plurality of slots in a delivery state. 2.The system of claim 1 where each of the plurality of struts and each ofthe plurality of slots are generally parallel to each other in adirection running along a longitudinal axis of the apparatus.
 3. Thesystem of claim 1 where at least one of the plurality of slots hasproximal and distal regions and a width at the proximal region isgreater than a width at the distal region.
 4. The system of claim 3where the stent comprises a widened securement region, where the widenedsecurement region comprises a width that is less than a width of theproximal region of the slot and greater than a width at the distalregion of the slot.
 5. The system of claim 4 where the stent furthercomprises a proximal extension disposed adjacent to the widenedsecurement region, where a width of the proximal extension is less thanthe width of the distal region of the slot.
 6. The system of claim 1where the enclosure is circumferentially rotatable relative to thecannula.
 7. The system of claim 1 further comprising a distal stopmember coupled to the cannula and positioned adjacent to a distal end ofthe enclosure, where the distal stop member allows the enclosure torotate relative to the cannula, but prevents the enclosure from slidingdistally over the cannula.
 8. A system for deploying at least a portionof a stent, the system comprising: a cannula having an outer surface; anauger having proximal and distal ends and a plurality of turns disposedtherebetween, where the auger is coupled to the outer surface of thecannula; a stent having a portion dimensioned to be disposed within avalley of the auger, where rotation of the cannula and the augeradvances the portion of the stent in a predetermined longitudinaldirection, an enclosure encircling the auger, and an atraumatic tipcoupled to the cannula, where at least a portion of the atraumatic tipis disposed beneath the enclosure, and where the enclosure can rotatecircumferentially relative to the atraumatic tip and the cannula.
 9. Asystem for deploying at least a portion of a stent, the systemcomprising: a cannula having an outer surface; an auger having proximaland distal ends and a plurality of turns disposed therebetween, wherethe auger is coupled to the outer surface of the cannula; a stent havinga portion dimensioned to be disposed within a valley of the auger, whererotation of the cannula and the auger advances the portion of the stentin a predetermined longitudinal direction; and an enclosure encirclingthe auger, where the enclosure comprises a plurality of struts separatedby a plurality of slots, and where the portion of the stent extendsthrough one of the plurality of slots in a delivery state.
 10. Thesystem of claim 9 where at least one of the plurality of slots hasproximal and distal regions and a width at the proximal region isgreater than a width at the distal region.
 11. The system of claim 10where the stent comprises a widened securement region, where the widenedsecurement region comprises a width that is less than a width of theproximal region of the slot and greater than a width at the distalregion of the slot.
 12. The system of claim 11 where the stent furthercomprises a proximal extension disposed adjacent to the widenedsecurement region, where a width of the proximal extension is less thanthe width of the distal region of the slot.
 13. The system of claim 9where the enclosure is circumferentially rotatable relative to thecannula.